Case hardening composition



hardened are submerged.

Patented May 21, 1935 UNITED STATES PATENT OFFICE CASE HABDENING COIPOBITION Artemas F. Holden, New Haven, Conn.

No Drawing.

Application December 15, 193:, Serial No. 643,413

e scum. (01. 148-15) k The present invention. relates to case harden use of the present compound with low carbon ing compositions which are adapted to become liquid when heated to a proper case hardening temperature and in which the metals to be case The composition comprising my invention'is one in which the materials are of such nature that the proper temperature to liquefy the composition and to cause case hardening to occur does not result in fuming whenin use, whereby desirable constituents of the composition are not are of such form as to present re-entrant angles in which it may be diillcult to thoroughly remove the case hardening compound when the case hardening operation is completed.

My composition is such that due to the fact that important parts of the composition are not given off as gases, the bath in which parts are case hardened need only be renewed to make up for mechanical loss of the composition which comprises the amount of the compound which adheres to the parts when they are removed from the bath. In other words, the bath is renewed by We mixture of all the constituent parts to' the extent of the mechanical loss during the use of the bath. .This is an important feature in that the relation of the compounds. in the bath does not become unbalanced by". the use of the bath.

The composition comprising the present invention is operated at working temperatures beneath 1700 F. and maysatisfactorily be used at temperatures as low as 1200 F. Preferably, however, better results are obtained by working between 1500" F. and 1650 F., the case hardening depth being more rapid at higher temperatures;

The present composition gives a deeper case hardening depth in a shorter time than has heretofore been attained in any liquid bath. In the use of case hardening compositions, a maximum depth is reached, which depth is not increased by an additional length of time that the parts are treated. The maximum depth heretofore has been approximately one-thirty-second of an inch in three hours, and involves the addition at fixed times of definite chemical compounds. The pres ent composition operates more rapidly than the known case hardenim' compounds and will produce a case hardening which reaches a maximum depth of about one-sixteenth of an inch. In the steel or suitable alloy steels low in carbon content, at a temperature of from 1600 F. to 1650 F. thecase hardening depth at the end of one half hour is substantially .008 to .012; at the end 5 of one hour, the depth is .015 to .022; at one and one-half hours, the depth of e the case hardening reaches a depth of .025 to .032; and at two hours, the depth is substantially .040 to .045.

In hardness tests, using Rockwell hardness, 0 scale, (the C scale is one in which a diamond point is used) is substantially as inflows:

Half hour '55 One hour p 60 One and one half hours 62 to 63 Two hours." 65 to 66 The preferred proportions and composition for my case hardening compound are as follows: 2o

' Pounds Sodium cyanide 9 Barium chloride 6 Barium carbonate.. & Calcium fluoride 2 The above compositions may be varied by equivalents and the proportions may be somewhat varied without departing from the present invention. I

* The'sodium cyanide content should not exceed forty percent of the entire composition and may be as low as fifteen percent of the composition to obtain satisfactory results. The composition may be produced by merely mixing together the above specified constituents or their equivalents without fusing. in which case, the user fuses the composition when the bath is heated. There is a slight fuming at the commencement of the fusing which. fuming very quickly disappears. The combined materials may be fused and then brokenup as a rough granular structure and transmitted to the user in this form. When so transmitted, the composition remelts at the temperatures specified without fuming.

What I claim is:

1. A case hardening composition adapted to form a case hardening bath for steel articles comprising the fusion of sodium cyanid barium chloride, barium carbonate, and calcium fluoride and with the sodium cyanide content being between the limits of fifteen percent to forty percent by weight of the total mass. I Y 2. A case hardening composition comprising the fusion of nine parts sodium cyanide, six parts barium chloride, eight parts barium carbonate,

we put: calcium mix? parts being designehed by wellht.

3 cuehudenlncompudtlon commslushy wdzhanlne parts sodium cyanle'e six parts banun; chibflde. eight parts barium carbonate and e tusedaw bath :orcaeehlmenmeon- ARTEMAB F. HOLDEN. 

